Automatic telephone system



M y 1950 J. M. BLACKHALL 2,509,415

AUTOMATIC TELEPHONE SYSTEM Filed March 19, 1945 9 Sheets-Sheet 2 FIG. 2

rank Un/Z' 5} um? INVENTOR 7% F6 JAMES M. BLAGKHALL ATTORNEY y 1950 J. M. BLACKHALL 2,509,416

AUTOMATIC TELEPHONE SYSTEM Filed March 19, 1945 9 Sheets-Sheet 3 FIG. 3 m I TesZ Trunk UniZ Uum'l ID 210 INVENTOR JAMES M. BLAGKHALL ATTQRNEEY May 30, 1950 J. M. BLACKHALL 2,509,416

- AUTOMATIC TELEPHONE SYSTEM Filed March 19, 19 15 9 Sheets-Sheet 4 FIG. 6

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Ellill llllflllfl nuuiluunnn INVENTOR JAMES M. BLACKHALL M y 1950 J. M. BLACKHALL 2,509,416

AUTOMATIC TELEPHONE SYSTEM Filed March 19, 1945 9 Sheets-Sheet e FIG. l3

: I9 I76 I73 /.90 67 INVENTOR JAMES M. BLACKHALL BY ATTORNEY y 1950 .1. M. BLACKHALL 2,509,416

AUTOMATIC TELEPHONE SYSTEM Filed March 19, 1945 9 Sheets-Sheet '7 a/ 23 FIG. 9 27 Trunk Uru'f Te'sl Unfi Termz'n/ a3 Assemb/ FIG. 11 230 36 FIG Q I f FIG. 1Q 2 246 249 243 cf; 24/ Z Z 4 250 243 k/Z 24/ W INVENTOR JAMES M. BLACKHALL g Y I:

ATTORNEY 9 Sheets-Sheet 8 Filed March 19, 1945 INVENTOR.

JAMES M ATTORNEY y 1950 J. M. BLACKHALL AUTOMATIC TELEPHONE SYSTEM 9 Sheets-Sheet 9 Filed March 19, 1945 INVENTOR. JAMES M. BLACKHALL ATTORNEY Patented May 30, 1950 UNITED AUTOMATIC TELEPHONE SYSTEM James M. Blackhall, Genoa, Ill., assignor to Leich Electric Company, Genoa, 111., a corporation of Illinois Application March 19, 1945, Serial No. 583,567

43 Claims.

This invention relates to signalling systems, and is particularly concerned with new and improved switching apparatus and circuits for use in automatic telephone systems of the general type disclosed in U. S. Patents Nos. 2,307,757 and 2,396,077.

The apparatus described in these patents is of a special type which may be referred to, for the sake of convenience, as crossbar switching apparatus. The principal features of these prior disclosures, and especially of the disclosure in Patent No. 2,396,077, are briefiy outlined below, for the purpose of supporting the understanding of the present invention which will presently be discussed in detail.

The line and test conductors are bare stripor bar-like members arranged in a bank, in a plurality of sub-groups. These members will be referred to as -bars. Assuming that the apparatus is used as a line finder, in a 100-line systern, and that there are in the exchange equipment two line conductors and one test conductor for each subscribers line, the line bank multiple of the switching mechanism will contain 100 sets of bars, each set comprising two line and one test bar and representing a subscribers line. There are thus 200 line bars and 100 test bars, or a total of 300 bars. These bars are arranged in vertically extending subscribers sub-groups each having lines, or a total of 30 bars. Ten such sub-groups are disposed vertically in parallel to each other.

A desired number of trunk lines may be provided, each having two line conductors and one test conductor. These trunk lines give access to equipment for completing calls. Each trunk line with its three conductors terminates in an individual trunk or bank unit which extends transversely of the bare strip-like conductors or bars forming the line bank multiple. Each trunk unit contains the switching means for selectively connecting any one set of three bars, representing the three conductors of any one of the 100 subscribers lines, with the conductors of the trunk line served by the trunk unit. The three conductors of the trunk line are for this purpose multipled to ten sets of extensions, each set having three extensions, forming in this manner ten sets of stationary trunk contacts each comprising three contacts.

' The switching means comprises in each trunk or bank unit a plurality of bank springs forming links or intermediate trunk elements, ten for each conductor of the corresponding trunk line, or a total of thirty intermediate trunk elements.

These trunk elements are disposed transversely of the line bank multiple in a plurality of horizontally extending vertically superposed levels. Each trunk element forms ten resilient contact fingers for selective engagement with the corresponding line and test bars, and an eleventh contact finger for connection with the corresponding stationary trunk contact.

Vertically extending, vertically movable tens actuators are provided, one for each subscribers sub-group of lines, or a total of 10 tens actuators. Each of these tens actuators is equipped with 30 projections for moving the corresponding resilient contact fingers of the intermediate trunk elements into engagement with the associated line and test bars.

The eleventh resilient contact finger of each intermediate trunk element is disposed near one edge of the trunk or bank unit. There are ten vertically superposed sets of such auxiliary eleventh fingers, each set comprising three fingers for coaction with associated stationary trunk contacts. One vertically movable units actuator is provided for each set of three of these auxiliary element contact fingers. There are thus ten of these units actuators and each is equipped with three projections for engagement with the three eleventh auxiliary contact fingers of the corresponding set of intermediate trunk elements, for the purpose of moving these contact fingers into engagement with their associated stationary trunk contacts.

A test unit is provided which is structurally similar to the trunk units, but is equipped only with tens actuators for operating resilient contact fingers into engagement with test bars of the line bank multiple. The test unit aids in the control of the operation of the units actuators in all the trunk units.

The connection of any one set of two line bars and one test bar, representing in the line bank multiple any given subscribers line, with the three conductors of the trunk line terminating in a given bank or trunk unit, depends on the operation of the proper tens actuator of such unit to connect the line and test bars of the line with the corresponding intermediate trunk elements, and on the operation of the proper units actuator of the unit to connect the auxiliary eleventh contact fingers of the selected intermediate trunk elements with the associated stationary contacts of the conductors of the trunk line.

In the apparatus made in accordance with the disclosure in Patent No. 2,396,077, the selection of the tens and units actuators is accomplished by a special selection control unit which is common to all the trunk or bank units of the apparatus. The selection control unit is equipped with means for selectively actuating tens and units selection solenoids which in turn operate associated tens and units selector bars. The selector bars extend throughout the switching apparatus, common to all trunk units, and aredisposed alongside and in parallel with the line bank multiple.

The selector bars of the prior disclosure are adapted to actuate clutches for coupling associated tens and units actuators in all trunk units with certain operating members individual to each unit. 'The operating members of one (idle) trunk unit are thereupon actuated by a socalled trunk or gate magnet and move the selected and coupled tens and units actuators to actuate the resilient contact fingers of the intermediate trunk elements for the purpose of completing the connection of the three line and test bars of a given subscribers line, with the three conductors of the trunk line terminating in the trunk unit.

The apparatus made in accordance with the present invention preserves and retains the essential features and advantages of the apparatus disclosed in Patent No. 2,396,077, as outlined above, and provides improvements which are valuable from the standpoint of manufacture and operation and which increase the flexibility of the apparatus and facilitate the maintenance thereof. Among the salient new objects and features are the following:

The present disclosure provides a switching; apparatus having bank or trunk units each equipped with individual or integral tens and units selection means. The common selection control unit of the prior disclosure and the common tens and units selection means thereof are eliminated.

The arrangement of the means forming in each trunk unit the conductors of the trunk line, which are multipled to the various levels of the unit, is simplified to eliminate numerous soldering points and to facilitate the manufacture, as well as the assembling and maintenance of the apparatus.

A new terminal assembly is provided, which comprises a terminal member removably attached to each trunk unit and common thereto, carrying tabs for receiving-all conductors for the trunk unit which radiate from a common cable, and having a, plurality of terminal sub-sections removably jacked to the common terminal member, each sub-section carrying the conductors which are individual to and are wired to certain predetermined operating sections of the trunk unit.

The overall improvement resulting from these and additional features, which will be broughtout in the detailed description, presents advantages which result in the use of smaller and more direct acting forces; elimination of close tolerances; lower initial tool investment and inventory of different parts; reduction to a minimum of time and skill for assembling, repair, removal or addition of parts of a trunk unit and of the trunk unit as a whole; and reduction of vulnerability to failure of each bank or trunk unit and its operating parts.

Details, including the aforementioned and additional objects and features, will be brought out in the course of thedescription of an embodiment of the invention which will be rendered with reference to the accompanying drawings. In these drawings,

Figfl is a diagrammatic. representation of a complete switching apparatus or mechanism constructed in accordance with the invention, showing its principal parts;

Fig. 2 illustrates a partial front view of the switching mechanism, with some parts in section and broken away to indicate details, showing one bank or trunk unit, the test unit of the apparatus, and the common terminal assembly. The combination may, for example, include the parts represented in Fig. 1 in prominent lines;

Fig. 3 shows a rear view of the apparatus illustrated in Fig. 2, with some parts in section and broken away to illustrate details;

Fig. 4 represents a top view of the trunk unit shown in Fig. 2 at the left and in Fig. 3 at the right, with parts broken away and in section to show details;

Fig. 5 is a bottom view of the trunk or bank Emit, Fig. 4, with parts broken away to show deails;

Fig. 6 represents a vertical section through the mechanism taken approximately along lines 5-6 in Figs. 1-3, with certain parts broken away to emphasize details;

line bank multiple at the trunk unit and adjacent test unit, showing also the terminal connections for the line and test bars;

Figs. 10, 11 and 12 illustrate details in connection with the new sectional terminal assembly provided for each bank or trunk unit;

Fig. '13 shows diagrammatically, on a somewhat enlarged scale, details of the structure of one of the units selection solenoids or magnets for coupling a units actuator with the operating member; and

Figs. 14 and15, taken together, represent a circuit diagram for the switching mechanism comprising a number of switching units when used to perform the functions of finder switches in an automatic telephone system.

The switching apparatus shown in Figv 1 comprises a base II on which are supported a plurality of trunk or bank units indicated by the numerals l-HJ, inclusive, a, test unit 12 and a terminal assembly IS. The test unit 12 and the terminal assembly l3 .are common to all the trunk units, of which there may be any desired number within practical requirements. Ten trunk units, are indicated in the drawings, which is assumed to be the full capacity of the base shown. A smaller number of trunk units .may be supplied, say six or seven, the [rest to be added as required. On the other hand, a longer base may be provided, having a capacity of fifteen or more trunk units in addition to the test unit shown.

It will be understood from the foregoing that the trunk units are individually removable and replaceable.

As shown in Fig. 1, the test unit I2 is located adjacent the trunk unit It. The test unit may, however, be located at any desired point, for example, at the extreme left of the switching mechanism in the. position occupied by the No.

I trunk unit. I

The complete "switching mechanism shown in Fig. l is assumed to'serve 100 lines and tohave trunkplines for connection with calling sub scribers dines. The r-nechanism may, of course, also be used to perform the functions of selector or connector switches.

There is a line bank multiple comprising ruetallic conductors in the form of bars or strip-like member-s extending lengthwise 'of the switching mechanism serially through the trunk units and the test unit thereof. Since there are three bars per line, twohrre barsanda testbar, the 300 bars constitute 190 se-tsof bars, three bars per set, and provide terminal facilities for 100 subscribers lines; When theswitching mechanism is used to per-form the functions of finder switches, it handles the outgoing calls .from a group of 100 subscribers lines which are connected to the line bars in the 100 sets of bars, respectively. -A similar arrangement is also disclosed in- Patent No. 2;r96,-0 ?7-.

Each trurik unit is provided with a trunk line terminating therein and includes switching means for connecting any subscribers line to such trunk line. For this purpose the subscribers lines are divided into ten subgroups of ten lines each, as in the case of mechanism shown in Patent No. 2g-396;0 i7; and each trunk unit is equipped with ten-intermediate trunk elements for each conductor or its associated trunk line, together with circuit-closing means so constructed and arranged that the line and test bars of each subscribers line in any sub-group may be connected to the intermediate trunk elements and any intermediate trunk element may be connected to the co rresponding conductor of the trunk line terminating in the trunk unit.

The operation of the circuit-closing means in each trunk unit is controlled by two sets of selection magnets or solenoids which are indii viduai to the trunk unit. There are ten tens selector solenoids and ten unit's selection solenoids. The tens solenoids are disposed in a transverse row near the top of the corresponding trunk unit, and the unit's-solenoids are disposed in a vertical rowan the front thereof. A gate or trunk magnet is provided on top of the trunk unit for the purpose of completing a connection as indicated by the operation of one of the tens selection solenoids conjunction with one of the units selector solenoids; The test unit cooperates in the control of the units selection solenoids.

It will be unde'rstoodpf course, that in the case of a small ekchange having less than 100 lines. the switchir-i'g xn'echanism need not be fully equipped. For example, in a (SO-line eXchange the switching rnechanismrequires only 60 sets of bars, or 1 80 bars altogether. The subscribers lines may be divided into six sub-groups of ten lines *each, or ten sub=groups of six lines each. The physical grouping of the sets of line and test bars in the line bank multiple corresponds to the grouping of the lines, and the selection solenoids and associated equipment correspondihg to "unused ths and units digits may be omitted. Thus, if there are only six sub-groups, only six tens selection solenoids are required, whereas if there areo'nly six lines per sub-group, only six units selection solenoids are required. The latter arrangement is generally to be preferried, since it requi'resdnly six sets of intermedi- 6 tion of one trunk unit will sufice. The unit de scribed below maybe trunkun'it No. It, or trunk unit No. I, orma'y be any one of the intervening trunk units 2 -9. The following detailed explan'a' tions refer to certain trunk units merely for the sake of convenience.

It mayalso be mentioned at this point that the drawings are not to scale, and that some of the parts are shown in a more or less schematic manner, and in certain instances somewhat dis: torted at the expense of'other parts,so as to bring out details.

Elements and features which may be presumed to be well known or which are'describ'ed in detail ihthe previously mentioned patents will be cov-' ei'ed herein onlyto' the extent which is necessary for conveying a clear understanding of what;

is new.

The supporting part of the trunk unit, as is particularly apparent from Fig. '7, is a frame similar to the one disclosed in the previously mentioned Patent No. 2,396,077. It comprises a rectangular lower portion having the sides l5-l6, a transverse bottom portion 17, and a transversetop portion l8. Thisrectangular part of the frame structure accommodates the mounting means for the line bank multiple comprising? the line and testba-rs, also the mounting means for'the ten tensselection solenoids and associated parts, and the'uriits actuators and coacting parts.- as well as the trunk and the wiring terminal means individual to the trunk unit.

Extensions I9 and 28 are mounted on top of the sides of the rectangular frame by means of pivot screws 2| which hold the reduced lower ends 2-2 of the extensions "at points in alignment with the horizontally extending transverse top part I8. These extensions accommodate the trunk oi gate magnet 2B5, certain operating means for the tens and units actuators, and contact sets indicated 2.112% and 221.

The mounting means for the line bank multiple comprising the 300 line and test bars comprises five plate-like mounting and supporting members made of insulating material, for example, Bakelite or polysterin, or other suitable insulating material. These plate-like membersaremounted in the rectangular frame defined by theside walls l-5-' -l 6 and bottom and transverse top portions li -I 8. Three of these members are indicated in the drawings, Figs. 6 and 7, by the numerals 232425. The member 23 is also visible in section in Fig. 3 and partially in section in Fig. 9. Each ofthes'e flve mountingmembers is pro-- vided with six horizontally extending, vertically superposed rows of rectangular tapered holes, the constricted part of the taper pointing the direction of the test unit and the flaring part pointing in the other direction. These five insulating members, each having sixty tapered holes, thus form thirty horizontally extending, vertically superposed rows of ten tapered holes each for the reception of th 300 line and. test bars.

The trunk units are arranged side by side, as indicated in Fig. 1, and the 300 tapered holes In the supporting and mounting plates in each trunk unit are therefore in alignment, longi tudinally of the apparatus, with the corresponding holesin themounting plates of all othertrunk units. The flaring side ofeac'h tapered hole is on the left of each trunk unit, as viewed in Figs. 1, 2 and 9. Therefore, theline and test'bars can be pushed in at'trunk unit No. I and successively through the corresponding tapered holesin trunk units 2 to 9, and finally through the holes in the plates 23-24-25 in trunk unit No. Ill. The test unit disposed adjacent trunk unit No. I9 is likewise provided with mounting plates such as 23-2 4-25, and the line and test bars are pushed through the corresponding tapered holes such as 34-35-36 just as in the case of the trunk units.

The arrangement is particularly apparent from Fig. 9, which shows part of the line bank multiple at trunk unit No. l0, part of the bank of the test unit, and also part of the terminal assembly for anchoring the line and test bars.

Numeral 23 in Fig. 9 indicates the uppermost insulating mounting and supporting plate indicated by like reference numeral in Figs. 3 and '1. Numeral 26 indicates a similar insulating mounting and supporting plate provided in the test unit, also shown in Fig. 3. Numeral 21 indicates an insulating plate which is part of the terminal assembly carried by the test unit l3 in Fig. 1. Each of these insulating supporting and mounting plates 23 and 26 is provided with siX rows of ten tapered holes each. The insulating plate 21 in the terminal assembly may be sectional or may be one large plate serving the entire unit. The line and test bars are pushed into place from left to right, as viewed in Figs. 1 and 9, and in reverse direction as viewed in Fig. 3, through the tapered holes in the successive insulating mounting and supporting plates of the trunk units. Line bars 28 and 29 and test bar 30 are thus pushed through the holes in the supporting plates in trunk units to 9, finally through the holes 3 I, 32, 33 in the uppermost insulating plate 23 in trunk unit No. I6, then through holes 34, 35, 36 in the similar supporting plate 26 in the test unit, and finally into engagement with the prongs 31-38, 39-40, 4|-42 in the insulating plate 21 in the terminal assembly. Terminal prongs 31 and 38 extend outwardly from the plate 21 forming a tab 43; prongs 39-49 extend likewise outwardly and form tab 44; and the prongs 4I-42 form tab 45. Each tab is anchored by a resilient extension indicated at 46, 41 and 48, respectively. Each test and line bar of the remaining 99 subscribers lines is put in place in a similar manner. The terminal assembly also includes the fanning plate I3, Figs. 1-3, provided with the usual holes for distributing the conductors which connect with the line and test bars through the medium of the tabs such as 43, 44 and 45, indicated in Fig. 9.

The numbering scheme is within certain limits a matter of choice. The present structure utilizes the scheme, also shown in Patent No. 2,396,077, according to which the line and test conductors are subdivided into ten vertically extending subscribers groups. The line and test bars of the first sub-group extend through the supporting plates 23-24-25, vertically near the front edge of the trunk unit (left in Fig. 6 and right in Fig. '7) They include the bars 28-29-39 at the top and bars 49-50-5I at the bottom. The line and test bars of the tenth or last subscribers sub group extend through the supporting plates 23-24-25 near the rear edge of the trunk unit (right in Fig. 6 and left in Fig. '1). They include the bars 55-56-51 at the top and bars 58-59-60 at the bottom.

' In the first vertical subscribers sub-group are the line numbers in the second group are the numbers 2 |-20; the identical numbering is continued throughout the intervening subscribers sub-groups; and finally in the last or tenth vertical subscribers sub-group are disposed the line and test conductors belonging to the subscribers lines Ill-B0. As shown in Figs. 6 and '1, the line and test bars belonging to the subscribers line No. II include the line bars 23-29 and the test bar 30. Subscribers line No. :2 is similarly represented by the three bars directly below the test bar 39. Subscribers line No. I6 is represented at the bottom of the first subscribers sub-group by the two line bars 49-56 and the test bar 5|. Subscribers line No. it, being the first on top of the second subscribers sub-group, includes the line bars 52-53 and the test bar 54.. Subscribers line No. 6| is represented by the line bars 55-56 and the test bar 51 in the last or tenth subscribers sub-group at the top thereof; and subscribers line No. 60 is represented by the line bars 58-59 and the test bar 66 at the bottom of the tenth subscribers sub-group.

Next to be described are the means forming the terminals of the conductors of the trunk line serving the trunk unit, and the intermediate trunk elements which are provided for selectively connecting any one set of line and test bars of a given subscribers line with the three corresponding conductors of the trunk line.

The soldering tabs in which the three conductors of the trunk line terminate are indicated in Figs. 2, 6 and 8 by the numerals 5|, 62 and 63. These tabs, as seen particularly in Fig. 8, are part of vertically extending strip-like members 54-65-66 which are disposed in" insulated relation to each other in a pile mounted on the wall 61 of a guard or guide member provided for the units actuators. The pile is mounted on a bottom plate 56 by means of a top plate 69 held by screws "all. Some of these screws extend through holes in the assembly for attachment thereof to the wall 61. This trunk terminal assembly can thus be individually manufactured as a unit, and can be attached to the apparatus and removed therefrom as a unit.

The three trunk terminal members 64-65-66, having the tabs 6|-6263, are each provided with ten extensions, thus forming ten sets of stationary trunk contacts, each set having three contacts. Three of these sets are indicated (Fig. 6) at 15-12-13, 14-15-16, and 11-18-19. These trunk contacts provide access to the corresponding conductors of the trunk line, for ten associated sets of horizontally positioned and vertically superposed rows of intermediate trunk elements.

Each intermediate trunk element or link memher is made of a strip forming ten contact fingers for selective engagement with associated line and test bars, and an eleventh contact finger for engagement with the associated stationary trunk contact. Thus, the trunk contacts 1I-12-13 project rearwardly and inwardly from the trunk conductor strips 64-65-66, at the top of the bank of line and test bars and provide access to the trunk conductors, for three intermediate trunk elements disposed at the top of the rectangular supporting frame. The set of trunk contacts 14-15-16 serve a set of three intermediate trunk elements disposed just below; and the trunk extensions or contacts 11-18-19 are provided for coaction with a set of three intermediate trunk elements disposed at the bottom of the unit.

test bars serving subscribers lines Nos. ll, 2|,

3|, etc., 9| and 6|. Similarly, trunk contacts 14-15-76 serve for connecting the line and test bars of subscribers lines I2, 22, etc. to 92 and 62; and the three trunk contacts "I'I- -lB-TB projecting from the trunk terminal strips 64-65-66 at the bottom serve to connect, with the conductors of the trunk line, the line and test conductors of the subscribers lines I0, 2!), etc., to 90 and IJD, which are disposed at the bottom of the bank.

The use of the trunkte'rrninal strips"64-65- -E6 and the stationary trunk contacts 'II-'I2--I3, etc., radiating therefrom constitutes a permanent multiple which is free of contact trouble and eliminates solderingpoints. The structure forms a compact sub-unit. Its use facilitates manufacture, assembly and maintenance.

Each of the intermediatetrunk elements comprises a strip made of insulating material having a tongue for insertion into a horizontal groove in the corresponding insulating supporting plate such as 23-24-25, and each is provided with a continuous strip of conductive material made of phosphor bronze or the like, which projects from the insulating strip and forms the resilient contact fingers disposed underneath associated line and test bars inparallel relation thereto. These intermediate trunk elements are similar in structure to those disclosedin Patent No. 2,396,077. For the sake of completeness, one of these elements maybe briefly described byreference particularly to Figs. 3, 6, 8 and 9.

The insulating strip of the topmost intermediate trunk element, inany given trunk unit, may be the one indicated by numeral Bil. This insulating strip is provided with a rearwardly projecting tongue 5!, Fig.9, which fits into the groove 8.2, Fig. 8, in the insulating supporting plate 23. The resilient contact fingers are formed integrally, e. g., from a strip of phosphor bronze. There are eleven such contact fingers extending from the insulatingmember '80. Four of these contact fingers are marked in Fig. 6 by numerals 83-35-85-8 5. The eleventh contact finger is not visible in Fig. 6, as it lies at the left of the contact finger 86 underneath the rearwardly extending portion of the stationary trunk contact 1!. However, part of this eleventh contact finger maybe seenin Fig. 8 at '1 I'a. The contact fingers of this particular intermediate trunk element serve the purpose of selectively extending the line bars in the topmost row oi the line bank multiple to the stationary trunk terminal contact TI. Thisincludes the line bars such as 28, 52 and E5. The eleventh contact finger Ha (Fig. 8) serves to connect with the trunk contact 1i radiating from the trunk conductor strip 56. The second intermediate trunk element comprising the insulating member marked in Figs. 3, 6 and 9 by numeral 81. It is constructed just like the first trunk element, and hasresilient contact fingers (In? in Fig. 9) pro jeoting forwardly underneath the second horizontal row of line bars, including the line bars 53 'Ihe eleventh contact finger of the second intermediate trunk element is disposed .iust underneath the stationary trunk contact member '52. The third intermediate trunk having the insulating member 88 in Figs. 6 forms similar contact fingers H38 underneath the test bars, including the test bars and and an eleventh contact finger just underneath the stationary trunk contact 13.

Therefore. any one set of the topmost line and test bars of subscribers lines disposed in the ten vertically disposed sub-groups of line and test contact fingers eleventh contact fintgers disposed underneath the stationarytrun'k contacts TI-'l8--l9. The trunk 10 bars of 1ines,such as "lines I 'l, 21 etc, to SI and BI may be connected with the stationary trunk contacts I I--"i2l'3, and thus with thetrunk conductors connected to the tabs 6|6263. The connection is obtained by selective operation of the corresponding set of the three vertically super posed contact fingers projecting from the trunk elements comprising the insulating members 80, 81, 88, and by actuation of theset of three associated eleventh contact fingers lying underneath the trunk-extension members or stationary trunk contacts 7 I, 52, I3, respectively. For example, the line and test bars of subscribers line No. 11 are connected with 'thetrunk conductors by actuation of the three contact fingers 86, I111, I108 of the "corresponding link members or trunk elements into engagement with the bars28, 29, '39, and by the operation of the eleventh contact fingers of those trunk elements into engagement with the stationarytrunk contacts 11,12, 13.

An intermediate trunk element such as described is providedunder each of the thirty horizontal rowsof line and test bars and each has an eleventh contact finger disposed underneath an associated stationary trunk contact. The lowermost set of line and test bars, which includes line No. I'D, 'representedbybars id- 50 5] and adjacent lines 29, 3! etc etc, andincluding lineIlIJ, represented by 'bars 5859-'60, maybe similarly connected with the trunk conductors by means of the intermediate trunk elements comprising the insulating members 9'9-9'I-92 (Fig. 6) and projecting therefrom, with element (having the insulating member 92) provided for coaction with the lowermost row of test bars, including test bars El and 60, is also shown in Fig. 5. It will be seen by referring to this figure that the eleventh contact finger 19a. is disposed just underneath the stationary trunk contact 19. This contact finger is operable by the lowermost projection of "the units actuator IIZ, while the remaining contact fingers of trunkelement 92 are operable by the lowermost projections carried on the tens actuators, including the tens actuators $5, 95, 134 and '91. p

The intermediate trunk elements are mounted alike, as described in connection withelement 86 having the insulating strip shown in Figs. 3, 8 and 9. Each insulating strip is anchored in its mounting plate by a tongue rearwardlyjorojecting therefrom into a groove providedin the mounting plate. In order to hold the elements in. position on the mounting plates, there a repro vided clampin'g means, comprising members I35 (Figs. 2, 5 and 8) and I35 (Figs. 6 and 10), one on each side of the frame and fastened thereto and having an angular projection which grips the ends of the insulating strips of the trunltel'ements and thus holds these elements "on the mounting and supporting plates. Resilient springlike fingers may be used in place ofeithe'r one or both o'f'these clamping I35 and I36 in accordance with the disclosure Patent No. 2,396,077. The clamping members i35-I35 may be made in secti if desired.

Ten tens actuators are provided for operating the contact fingers of the intermediate trunk elements into engagement with associated line and test bars. There is one tens actuator for each vertical row or sub-group of line and test bars, representing ten subscribers" lines, and each such tens actuator has thirty projections for operative engagement with the thirty contact fingers of the intermediate trunk elements disposed underneath the line and test conductors of each sub-group.

Each tens actuator is arranged and constructed similar to the tens actuators disclosed in Patent No. 2,396,077. It comprises a vertically extending, vertically movable bar carrying five insulating members molded on it, and each insulating member has six projections for engagement with .six contact fingers of vertically correspondingly placed trunk elements. The bars are movably mounted at the bottom of the structure in a removably mounted journal plate I3! (Figs. 5 and 6) and extend upwardly alongside the corresponding vertical rows or sub-groups of line and test conductors representing the subscribers lines. Thetens actuating bar 95, Figs. 5*, 6, 7 and 9, is thus provided for operatively actuating the contact fingers of the intermediate trunk elements into engagement with their associated line and test bars representing the first sub-group of lines, i. e., the subscribers lines I I to III, which includes line bars 28-29 and 4959 and test bars 30 and 60. The second tens bar 96 serves for operatively actuating the contact fingers of the intermediate trunk elements into engagement with the line and test bars in the second sub-group of subscribers lines, numbers 2I-'2Ii, which includes the line bars 52 and 53 and the test bar 5 Tens bar I34 in Figs. 5, 6 and 7 is provided for actuating the contact fingers of the intermediate trunk elements into engagement with the line and test bars of the eighth sub-group, representing subscribers lines 8 I8!l; and the tenth tens actuator bars 55-56 and 58-459 and the test bars 5! and As previously mentioned, each of the tens actuator bars is provided with five insulating members molded thereon, each insulating member carrying six projections. These projections underlie the associated. res lient contact fingers of the intermediate trunk elements disposed in the corresponding vertical sub-groups. Three of the five insulating members carried by the tens bar 95 are indicated by the numerals 96, 99, I69. Three of the insulating members carried by the tens bar 96 are indicated by numerals IliI, I62 and I63; and three of the insulat ng members carried by the bar 91 are marked by numerals I64. I95 and I66.

The connection of any one set of line and test bars belonging to any given line is dependent on the tens selection, that on moving the corresponding tens actuator bar upwardly so as to actuate the resilient contact fingers of the corresponding intermediate trunk elements into engagement with the line and test bars through the medium of the projections extending from the insulating members of the associated tens bar. For example, if it is desired to connect contact fingers 86, 567, I68 (Figs. 6 and 9) of the intermediate trunk elements comprising the insulating strips 89, 87, 88 with. the line bars 28?9 and the test conductor 39, respectively, of subscribers line No. I i, it will be necessary to lift the tens bar 95 upwardly so as to allow the pro ections I 19. II 6 and Ill on the insulating member Iiifl, Fig. 9. which are mold d on the tens bar 95. to lift the contact fingers 96, Ill! and I68. The line and test conductors of the subscriber line II are then extended to thetrunk terminal assembly by way of .the corresponding intermediate trunk elements.

This does not complete the connection because it is also necessary to operate the eleventh contact fingers of these intermediate trunk elements into engagement with the associated trunk contacts 'I|-I2-'I3, which is accomplished by the operation of a units actuator yet to be described.

The actual operation of any one of the tens actuator bars is preceded by the tens selection, which will be explained lateron: Completing the description of the physical structure of the tens actuators and associated parts, reference is again made particularly to Fig. 6 which indicates a clutch housing on top of each tens bar. Thus, there is a clutch housing carried by the tens bar 95, as indicated at I I5. Theclutch housing of the tens bar 96 is indicated at H6; that'of the tens bar I34 is shown at I33; and the clutch housing of the last tens bar 91 is indicated by numeral III.

The clutch housing for each tens actuator is similar to the one described in detail in Patent No. 2,396,077. It is provided with a recess containing a coiled spring anchored in the housing at one end and radially extending therefrom at the other end. A lifting pin projects into each clutch housing from the top. Thus, as shown in Fig. 6, lifting pin I I8 projects into the clutch housing II5 of the tens bar 95; lifting pin H9 extends into the clutch housing I I6 of the tens bar 96; lifting pin I32 coacts with clutch housing I33; and lifting pin I29 extends into the clutch housing II! of the tens bar 97. The other lifting pins shown in Fig. 6 project similarly into the remaining associated clutch housings.

Each lifting pin extends upwardly through a hole in the armature I38 of the trunk or gate magnet 205 and is held from dropping out of the armature by a head or enlargement. The heads of pins H8, H9, I32 and I20 are indicated at I39, I 46, MI and I42, respectively. Each pin is rotatable within its hole and is provided with a tens actuators, are guided in a horizontally disposed shelf member 266 in back of the guide and lock member I41.

The spring in each clutch housing is normally recoiled and open, permitting the associated lifting pin to move freely upwardly without at the same time lifting the clutch housing and therewith the associated tens bar. However, when a sprin is tightened around its associated lifting pin, and the pin is then lifted by the armature I38, responsive to energization of the trunk magnet, it will lift the clutch housing and also the corresponding tens bar. The lifting of the remaining pins by the armature will have no effect on the remaining tens bars which have not been coupled by the tightening of their associated clutch springs. The "tens selection, that is to say, the tightening of the clutch spring in any one of the clutch housings for the purpose of coupling atens pin with its tens bar, is accomplished electromagnetically by the tens solenoids or magnets which will be explained with reference to Figs. 2-4, 6 and 7.

There are ten tens selection solenoids, one for each of the ten clutch housings associated with the ten tens actuator bars. Solenoid I25 is provided for selecting the operation of the tens actuator bar 95 by tightening the spring in the clutch housing II5 around the lifting pin H8. Similarly, solenoid I26 is provided for selecting the "op ation of tens actuator bar 96 by tightening the spring in theclutch. housing H61 aroundthe lifting pin H9; Thesameis true of the remaining solenoids, including the solenoid. I21 which serves to tighten the clutch spring in the clutch housing III around thelifting. pin I23 so as to select and condition the tens actuator bar 91: for lifting when the lifting pin I2!) is displaced upwardly by the armature I38 of the trunk magnet.

The solenoids are mounted in a suitable channel member, indicated in Fig. 7 at I28, and each solenoid has a plunger such as I29, indicated in Fig. 4, in connection with the solenoid I39. The plunger I29 is adapted to tighten the spring in the clutch housing I33 by moving its free end I3I, thereby tightening the spring around the lifting pin .ISZ. The plungers of all the solenoidscoact similarly with the coiled springs in the associ-. ated clutch housings of the corresponding tens. actuator bars.

The free ends of the solenoid plungers are guided holes such as I3,Id i-i-'i5-1I4t a tens guide and lock member Ml, Figs. 4 and 6', which is a strip-like structure supported at each end in the mountings I48 and M9. The latter are secured on the frame by means of arms I50 which underlie the upward frame extensions I91 and 29. The tens actuator guide shelf or plate 2% extends between the arms I56, as seen in Fig. 7.

The strip-like guide and lock member i571 carries a number of. projections f'ormi 3 locking cams I5II52I53, 4. There is one such locking cam for each tens actuator clutch, and each locking cam is positioned just above the free end of the clutch spring projecting radially from the corresponding tens actuator clutch housing. Thus, the free end I3I of the clutch spring radiating from the clutch housing I 33, which coacts with the lifting pin E32, is positioned just underneath the locking cam I52. Accordingly,- assuming that the solenoid I35 in Fig. 4 is energized and attracts its plunger I29, this plunger will move the free end I3! of the clutch spring disposed in housing I33, so as to couple the clutch. housing, and therewith the tens actuator rod I3 8, with the lifting pin I 32. The free end i3l of the spring is thereby movedfrom underneath the cam I52 into vertical alignment with the upwardly extending inner edge thereof. The gate or trunk magnet 285 is then energized in a manner which will be presently explained, attracts its armature 533 (see Figs. and '7), and moves the liftin pin I32, and therewith the clutch housing I33 and the tens actuator rod 3 3, upwardly to move the resilient contact fingers of the various intermediate trunk elements into engagement with the line and test bars of the corresponding vertically disposed sub-group of subscribers lines. Tens actuators which have not been coupled by their clutches with their corresponding lifting pins remain in normal position. The free end I3I of the clutch springcoacting with the lifting pin l32, which has been moved to the edge of the locking cam I52 upon attraction of the plunger I29; is moved incident to the lifting of the tens actuator along the edge of the locking cam, and is thus locked in operated position, restin against the edge of the locking cam. Subsequent release of the solenoid I3 is ineffective to release the clutch spring within the clutch housing of the corresponding tens actuators. The tens actuator will remain in operated position so long as the gate or trunk magnet $5 is energized. Release of the operated tens actuator is accomplished by deenergiz-- ation. of the trunk magnet. The operation. 83p: plies, of course, to each and every one of" the tensactuators.

The rod-like element 26-! mounted in thememe bers ma. |49 in back of the tens guard and locking plate I41. serves as a stop for limiting the outward displacement. of the plungers of. the tens solenoids.

As previously stated; there are ten. units. ace tuators, one for operating. each. of the ten sets of eleventh. contact fingers of: the intermediate trunk elements into engagment with their 8550-. ciated' sets of stationary trunk contacts. Each such units actuator is. made of suitable insulate ing material, e. g., Bakelite, and comprises, as particularly shown. at the bottom of Fig. 8, a housing I55, which is rounded at one side and flat at the other, and is provided with a recess I56 forming a. chamber. In this chamber is. dis.- posed, a coiled clutch spring. One end. of the spring is anchored inv the housing I55, and the free end I51 projects therefrom. The 111111752107 tuator alsohasa guide extension I58. and three projections or prongs. I. i9.-.I.6.il:.I5I; The units actuators, including the actuator I55, are freelymovable on the units actuator lifting rod I62. They. do not normally follow an upward dis.-. placement of the lifting rod except for. that units actuator which is coupled to the lifting red. by the tightening of its clutch spring. The operation is. similar as in. the. case of the clutches for the tens actuators.

The guide portion I58 of. the. units actuator is disposed in a. guide opening or slot in, the rear wall I63 of the units guidemember; The. guide is mounted in front ofthe. switch structure by an. extension I54 The three. projections; [SQ-e I6il-.I I. of each units: actuator thus extend rearwardly, as seen in Fig; 8,, through the. wall; I63 of the guide, underneath a corresponding set of three auxiliary eleventh contact fin ers oi as.- sociated intermediate trunk elements. For ex.- ample, theprojections I5S:...IE.I1 oi the units. ace tuator I55 shown in Fig. 8 underlie the eleventh contact fingers I65.I:t5.|51. Assuming now that the units actuator I55, Fig. 8, is coupled to the lifting rod I52 by its spring Isl, and further.- assuming that the lifting rod is, displaced upwardly, it will be clear thatthe projections. I59-. IfiI: will: move the eleventh contact. springs IE5-..I 6.1 to connect these springs with the eta.- tionary. trunk contacts 2t.32.5.9-2l fi.. The three intermediate trunk elements associated with the three eleventh contact fingers I65 l 66' I51, arethus connected with the three trunk contacts 258e-e2i39ee216 extending from the trunk terminal strips 6d'65-5.5 in the same manner as the trunk contacts I I--'i2.-l31 extend from these strips.

Ten such units actuators. coact with the lifting r0d I iiZ. The uppermost tens actuator is marked by numeral Hi8; It is adapted to connect the eleventh contact fingers of the intermediate trunk elements comprising the insulating members ass-niece into engagement with the sationary trunk contacts 'EI- EZeJZ-E. Thus, if the line and test conductors 01" anyone of the subscribers" lines in the: toplevel of the trunk or switching unit, including the lines Nos. II, 2I', etc, etc., to No. BI, are to be connected to the trunk such connection is accomplished, first; by the operation of the corresponding tens ac tuator which serves the particular subgroup. of lines, and second, by the operation of the units actuator I58 which serves to connect the eleventh contact fingers of the corresponding intermediate trunk elements with the stationary trunk contacts 'II1213. The units actuators I69, I18, I55, I'll, I12 (see also Fig. 2) serve in a similar manner for connecting the vertically successively downwardly disposed sets of eleventh contact fingers of the corresponding intermediate trunk elements with the associated stationary contacts of the trunk line.

There is one units solenoid provided for controlling the operation of each units actuator. Solenoid I13 controls the operation of the units actuator I68; solenoid I14 controls the operation of the units actuator I69 and so on; and the lowermost or tenth units solenoid I15 controls the operation of the units actuator I12. The solenoids are mounted in a channel member I16 which is attached at the front of the trunk unit, as is particularly apparent from Figs. 2, 5, '7 and 8. Each solenoid has a plunger, such as I11, coacting with the units actuator I68, the plunger having a reduced extension I18 which projects through a guide opening in the wall 61. Each plunger is also provided with an opening through which projects the free end of the corresponding clutch spring disposed in the associated units actuator housing. For example, as shown in Fig. 8, the free end I39 of the clutch spring within the units actuator I68 projects through the hole I8I in the plunger I11.

The wall 61 of the units actuator guide is provided with a number of cam-like extensions, the top extension being marked in Figs. 2 and 8 by the numeral I85. There are ten such cam-like extensions on the units actuator guide, one for each of the units actuators. The displacement of the free end of the clutch spring in each units actuator, by the associated solenoid, prepares for a locking operation which is completed by the upward movement of the corresponding units actuator responsive to the actuation of the units lifting rod I62 responsive to the energization of the gate or trunk magnet 285. The free end of the clutch spring will then slide upwardly along the edge of the associated locking cam such as I65, and will remain in this position even subsequent to deenergization of the corresponding units solenoid. Release of any upwardly displaced units actuator follows the deenergization of the gate or trunk magnet 285. The operation is similar to the locking and release action of the cams described in connection with the clutches which control the tens actuators.

The structure of one of the units solenoids, for example, solenoid I13, may be described with reference to the more or less diagrammatic representation shown in Fig. 13. Numeral I16 indicates the channel member for mounting the solenoids. The solenoid spool I99 has the usual flanges between which is provided the solenoid winding I13. The structure is mounted by means of a screw I92 which is provided at its forward end with a recess I93. The plunger I11 extends into the structure, as shown, and is provided with a recess I95. Within the recesses I93 and I95 of the screw extension and of the plunger is disposed a spring I96. The plunger I11 therefore always has a tendency to move outwardly to the right, as shown in Fig. 13. Its motion is limited by the side wall 61 of the units actuator guide. The reduced portion I18 of the plunger extends through the hole in the wall 61, as previously described. Numeral I8I indicates the opening in the plunger I11 through which extends the free end I 89 of the clutch spring associated with the units actuator I68. It should be observed that the opening I8I in the plunger is relatively large as compared with the diameter of the clutch spring I88, and that the spring is normally disposed within the opening I8l near the bottom thereof. Upward displacement of the units actuator with its housing and the clutch spring moves the free end I88 of the clutch spring from the position shown in Fig. 13 in full lines upwardly to the position shown in dotted lines. The tension of the clutch sprin also tends to bias the solenoid plunger outwardly. This action is supported by the action of the spring I96. Any tendency of the plunger to stick is thus counteracted. The tens' solenoids are constructed similarly.

The units actuator or lifting rod I62 is movably journalled at the bottom in an angular extension or ear I91 projecting from the side wall 61 of the units actuator guide and is similarly journalled at the top of the guide in an extension or ear I98. The lifting rod is provided at the lower end with a washer I99, and a spring 280 is interposed between the washer and the journal member I91, for the purpose of biasing the actuator rod normally downwardly. A bead 28I is provided on the rod I62 for the purpose of keeping it in position during the assembly of the mechanism. The bead prevents the slipping-out of the actuator rod under the force of the spring 280 at a time when certain operating means, yet to be described, are not effective.

The gate or trunk magnet comprises the coil 285 having a core 286 on which are mounted the heel-pieces 201, 299. The core, with its heel-pieces, and the coil are mounted in the upright extensions I928 by means of the pivot screws 299-2). Screws 2II2I2 serve to hold the heel-pieces 291-498 in position.

The armature is an angular structure having the arms 2I32I4 which are rotatably mounted in the upright extensions I92!) by means of pivot screws 2I52I6. Extensions 2I12I8 connect the armature proper I38 with the arms 2I32I4. The armature member I38 is provided, as will be remembered, with the holes through which project the lifting pins such as H8, H9, etc., which extend downwardly into the corresponding tens actuator clutch housings H5, H6, etc. A heel-piece 229 is provided on the lower side of the armature I38, its opposite ends projecting from the armature into alignment with the heel-pieces NIL-208, respectively. Energization of the coil 295 of the trunk magnet results in swinging the armature in counter-clockwise direction, as seen in Fig. 2, and in clockwise direction, as seen in Fig. 3. This motion results in upward displacement of all the tens lifting pins II8, II9, etc., up to and including liftin pin I29. Only that lifting pin is effective to lift its associated tens actuator which has been coupled by the clutch spring actuated by the associated tens solenoid.

The armature I38 is also rovided with an operating member for the units lifting rod I 82 which is in the form of an angular arm 22I having an extension 222, The latter is slotted for the reception of the units lifting rod I62 just below the bead 223 formed on the rod. The rod I62 thus normally rests with its bead on the extension 222 of the armature, being biased in downward direction by its own weight and by the spring 208 at the lower end thereof.

It will be seen from theforegoing that attraction of the armature I38 responsive to energization of the trunk magnet 205 results in upward displacement of all the lifting pins provided for the tens actuators and also upward displacement of the units actuator lifting rod 162. Thisoporation in turn .liftinginto operated position that tens actuator which has been coupled by its spring clutch with itsassociated iii-ting pin, and also that units actuator which has been coupled with the units lifting rod I 62 by its associated clutch spring. Operative actuation of the trunk magnet 205 is preceded by the selective actuation of one of the tens solenoids and one of the units solenoids.

For example, if the line and test bar-s 28-29-3fi of subscribers line No. II are to be connected with the trunk conductors, it will be necessary to operate tens solenoid 4-25 so as to couple the lifting pin H8 with the clutch housing H carried by the tens actuator rod 95, and also to actuate solenoid I13 soas to couple theunits actuator-l58 with the units lifting rod 462. Subsequent en ergization of the trunk magnet 205 then lifts the tens actuator rod- 95, effecting engagement of the resilient fingers 86, 1-01, N18 with the line and test bars, respectively,-of thesubscribersline I l, and also lifts the units rod Hi2, therewith the units actuator 168, to connect the eleventh contact fingers on the corresponding intermediate trunk elements with the stationary trunk-contactsll, 12, 13. The operation as described completes the connection of the line and test "bars of line No. I I with the conductors of thetrunk line.

A strip or plate-like "cross-piece *225 is provided on topof the structure andconnects the upward frame extensions 19, 20. Attached to this piece are contact sets 226-227, as shown in the drawings. The contact springs of these sets are operated by the bridge member 21-! on top ofthe units lifting rod I62, which is loosely fitted on the units rod 162 so as to permit free angular motion of'this rod. The free angularmotion, i. e., possibility of rotationof the units lifting rod-and also of the tens lifting pins is desirable and 'of practical importancefor the proper operation and the life of the clutch'springs. The eontact'pressure is propagatedto the lifting rod and assists the downward bias thereof.

The new terminal assembly provided for each trunk unit is best explained with reference to Figs. -12, inclusive. It will be recalled that the clamp member I36 holding the insulating strips of the intermediate trunk elements in-posi tion on the mounting 'andsupporting plates is attached to the side wall l5 of the frame'ofthe trunk unit. Referring to Fig. 10,15shows'the side wall of the frame in section, numeral 23 isthe uppermost mounting and supporting platefor theline and test bars; and numeral 80 represents theuppermost intermediate trunk element or, rather to say, the insulating strip thereof. At 83 is-indicated one of the resilient contact fingers extending from the strip 8|].

The new terminal assembly comprises a T-shaped member having a base 23B and a rib 23! centrally projecting therefrom. ThisT-shaped member, with its base and its .central rib-like projection, is made in one piece and extends vertically substantially throughout the height of the rectangular frame of the trunk unit 'at the rear thereof. See also Figs. 4, .5, 6 and 'Z. This T-shaped terminal memberiis suitably attached to the side oithe frame or, rather to say, to the clamp member 136.. Theileftedge of thelbaselSO, asseen in Figs. .10..and=.11, is provided with fanningslots i232. Inback of theassembly may .be placed thecable 2-33 which carries the conductors for the. correspondingtrunk iinit. Thewires extending .from .thecazble. 235% are iannedthrough thezslots 232, .as indicated in connection with the wire 234 shown Fig. 116). The central rib 52311 is provided with conductive. tabsmaisfi, asmany as may :be requiredi for. the. trunk unit each tahiorniing atthe left, Figs. ill-and .1 1, asoldering terminal for the attachment-oi the'wires such .asL234,- and at the right an-extension projecting from the rib 231, each extension iunctioning in the manneriof a jack terminal. Each wire .coming from the cable 233 is individually fanned into-a correspending fanning slotiaz-and is soldered to one ofthe s01deringtabS-235. The member .2230 with its central rib 23i .formslthe terminal strip which is individual to the trunk limit .and receives all the wires f or the unit.

Inasmuch as there are three principal operating sections to be considered in the presentinstance, in connection with each trunk unit, itis desirable to place the incoming and outgoing conductors terminating in the cable 233 in such a mannernnthe terminalstrip 23E! thatall wires or conductors .tor the respective sections of the trunk unit are disposed adjacent to each other, forming distinct groups. Thus, the wires for the units solenoids may be placed on the terminal stripifiil at a definite section thereof; the wires for the. tens solenoids at another section; and the wires for the trunk magnet and for the contact springs on top oi the unit maybe placed in a third definitesectionmf the terminal strip 230.

Sectional terminal strips are provided for ooaction with the groups or sections of wires on the principal term-inal strip 2%. There are in the present instance three sectional terminal strips 2%, 2M and 242, as seen in Figs. -6 and "7. Each is individual to a definite operating section of the trunk unit. "Forexample, the topsection ne may be individual-to thetrunk magnet and to the 1 spring assembly; 1 the terminal section 255 maybe individual to thetens actuator solenoids; and the terminal section 2242 may be individual to the units solenoids.

Each section-a1 terminalcomprises a T-s-haped member, as indicated in Figs. 10-1-2; its base having at one edge the fanning slots tisfiigs. 11 and 12, and its central =rib being provided with legs such as.244, Figs. 10 -and"l2. These legs areinserted insiots such -as 2-"45--2"4B-2 ll in the right edge 'of the base 235 of "the "principal terminal strip. Each of the sectional terminal members E li-2d 1-2412 is prov-ided with -a numberof conductive tabs forming at one side of its central-rib prongs 249, for engagement with the jack-like extensionsof theconductive tabs 235 of the -prin cipal terminal member, and soldering terminals 268 on the other side, to which may be soldered the ends-of the wires'which extend to the cor responding operating parts of the section served by the individual sectional strips zit-2d l--2 i2, respectively. The sectional terminal members are thus constructedsimilarly, but serve different operatingsectionsof the'swi-tching unit. The cable leading from the terminals 2*4B to the corresponding section of "the apparatus which is served by the sectional terminal 240 is indicated at 256. The cable individual to the terminal section 24 l is indicated at 25!; and the cable individual to the lowermost section M2 oftheterminal is indicated at 252.

Each section of the trunk unit can thus be individually wired and provided with a sectional terminal strip such as 240--24I242. All the wires are brought into the unit by the cable 233 and are fed to soldering tabs 235. The common terminal 230 with its wires can be attached and removed as a unit. After the various sections of the trunk unit are put in place and properly adjusted, the wires of each unit being connected to individual terminal sections, such sections are put in place simply by jacking them into position as described and as is apparent from Figs. -12.

The testunit of the mechanism is common to all the trunk units and is constructed similarly. It is provided only with intermediate trunk elements for coaction with the test conductors in the various levels. The arrangement is apparent from Figs. 3 and 9. Accordingly, only tens actuators are required, as indicated in Fig. 3. The placement and operation of these tens actuators corresponds to that described in connection with the trunk unit. The test unit therefore also carries the tens solenoids described in connection with the trunk unit, each solenoid adapted to couple a certain lifting pin with a spring contained in a clutch housing of each tens test actu ator. One such lifting pin 254, extending into a clutch housing 255, is shown in Fig. 3, the clutch housing 255 being connected with the tens actuator rod 256. Each tens rod is provided with members such as 2'i5, each carrying a number of projections just as the corresponding actuator members provided in each trunk unit. Only every third projection is efiective however, to actuate a contact finger on the associated intermediate trunk element into engagement with a test conductor. The contact finger 216, Figs. 3 and 9, projecting from the insulating member 27'! serves the test conductor 30 of subscribers line H.

Units actuators are not required in the test unit, but solenoids 25l2582592BU--2Bl may be provided in their place, as shown in Fig. 2, which may correspond in structure to the solenoids Il3ll5 in the trunk unit. The function of these solenoids is, however, different. They are used or may be used, if desired, in the manner of ordinary relays operating suitably formed contacts indicated in Fig. 2 by the numerals 26L- 263-264-265. If desired, these relay solenoids may be omitted.

The structure and assembly of remaining parts of the test unit are in all other respects similar to the structure and assembly of corresponding parts of a trunk unit. This applies to the frame as well as to the trunk or gate magnet, to the tens test solenoids, the armature, and to the general features of the contact sets on top of the test unit.

The foregoing description completes the explanations with reference to the physical structures of the various parts of the apparatus. It is desirable to point out certain features directed to the assembly and adjustment.

The manner of assembly, attachment or removal of the parts which are disposed on the outside of the switching units will be sufiiciently obvious so that no detailed explanation seems to be required. It will be clear, for example, that any trunk operating magnet assembly can be removed after taking out the pivot screws for the operating magnet armature yoke and the screws which hold the frame extensions 19-20 to the frame.

Any line or test bar may be removedfrom the line bank multiple by simply pulling it out at the left end of the switching mechanism as shown in Fig. 1. To replace a bar, it is pushed in until the end is gripped by the terminal at the termi: nal assembly l3 disposed at the right of the apparatus. The removal, for adjustment, repair or replacement, of an intermediate trunk element, from any one trunk unit, is briefly explained below.

It may be assumed, for example, that it is desired to remove the uppermost trunk elementassociated with the insulating member 80. The sectional terminal strips 240242, Figs. 3, 6 and 7, are first detached from the common terminal strip 230. The common trunk terminal strip 230 is then removed as a unit by removal of the corresponding screws which hold it at the side of the frame. See Figs. 3, 4, 5 and 10-12. The clamp members I35, I36, best seen in Figs. 8 and 10, are then partially detached by loosening the corresponding screws which fasten them to the frame. Loosening of one of these clamp members at one side of the trunk unit may be sufficient. In case spring clips are used in place of these clamp members or in place of some of them, such as shown in Patent No. 2,396,077, the spring clips are, of course, loosened or removed. The corresponding trunk element with its insulating member, e. g., the member may now be disengaged from its slot 32 in the supporting and mounting plate 23 (see Figs. 8 and 9) and could be withdrawn from the switching mechanism at the rear except for the fact that the tens actuators are in the way. This difficulty is provided for by arranging the parts so that the tens actuators may be moved to the right (Fig. 2) far enough to clear the ends of the contact fingers on the trunk element. In order to accomplish this, the pivot screws 2l5-2l6 for the armature are turned out far enough so that the heads thereof are outside their bearings. The trunk magnet armature yoke may now be moved to the right, as seen in Fig. 2, far enough to carry the tens actuators out of the way. It will be noted in this connection that the frame extensions ill-2i] have slots in which the pivot screws 2l5--2|6 can move sideways. It should also be noted, as seen in Fig. 7 that the member 222, which operates the units lifting rod I62, has an open slot through which the lifting rod extends. The lifting rod therefore does not interfere with the described movement of the armature yoke.

The trunk element may now be removed for adjustment or repair, and may then be re-inserted or another trunk element may be put in its place, after which the parts which were removed or displaced are reassembled in their proper positions. Any intermediate trunk element can in this manner be taken out for repair or adjustment, or for replacement by another element.

A complete trunk unit may also be taken out if it should become necessary or desirable. This operation is briefly explained below.

It may be assumed, for example, that it is desired to remove the No. 5 trunk unit, Fig. 1. The trunk terminal sections 240-44 l-242 are first removed from the common trunk terminal 23023I of this unit. This is done simply by pulling out each section 240--24|-242, thereby disconnecting the jack prongs of the removable sections from the conductors carried by the central rib 23! of the common terminal strip 230. See Figs. 4, 5 and 10--12. The common terminal strip is then removed from the trunk unit. This leaves the trunk unit free for removal together with its terminal sections 24ll--24|-242, except for the fact that the line bank multiple formed by the line and test-bars extend through the trunk unit. These bars are withdrawn, toward the left as seen in Fig. 1, far enough so that the right inner ends thereof clear the N0. unit. They neednot be entirely withdrawn.

The No. 5 trunk unit may now be lifted out after first removing screws which attach it to the base N. If the trunk unit is being taken out for repairs, it will be replaced after repairs are made. Otherwise a new trunk unit may be inserted, or if none is available, the switching mechanism may be reassembled Without the No. 5 trunk unit. The procedure is the same if one or more new trunk units are to be added to a switching mechanism which was previously installed without the full equipment of trunk units; that is, the line and test bars have to be withdrawn to permit the removal or insertion of one or more trunk units, if desired.

The manufacture and assembly of parts is greatly faciiltated by the unitary structure and arrangement of coacting sections of the switching units. For example, the units solenoids are mounted on the channel member H6, and all these solenoids and supports therefore can be manufactured and assembled as a sub-unit, and

such sub-unit can then be put in place in an obvious manner. The same applies to the tens solenoids which are mounted on the channel member its and supported as a unit on the shelf 256.

The trunk terminal assembly forming the stationary trunk contacts throughout the various vertical levels of each trunk unit is likewise manufactured and put in place as a unitary subassembly. The multiple is formed simply by conductive strips which are assembled, in a pile, with insulating strips between the conductive parts, as previously explained, and is particular- 1y apparent from Figs. 2 and 8.

The advantages resulting from the structure of the individual sectional trunk unit terminal provisions (see Figs. 35 and -12) are, it is believed, obvious. The conductors incoming to the trunk unit and outgoing from it are not wired into the unit in the usual sense, requiring the carrying of each wire to its terminal point, but are Wired to the terminal strip which is individual to each trunk unit and carries all the Wires common thereto. This strip is removably attached to the trunk unit. Individual operating sections of the trunk unit are wired to individual sectional terminal strips which may be removably attached (jacked) to corresponding sections of the common terminal strip. The arrangement facilities all steps in the production, assembly and maintenance of the apparatus.

Figs. 14 and 15 taken together, with Fig. 14 placed on top of Fig. 15, show a circuit diagram for the described switching mechanism when it is used to serve as a group of finder switches for connecting calling subscribers lines with trunk lines. The diagram is intended for explanatory purposes only, to support the understanding of the mechanism and its operation. Therefore, details such as transmission of the dial tone, provisions for party lines, and certain supervisory circuits and the like have been omitted, and some of the individual circuit elements have been simplified so as to keep the drawings clear and to facilitate explanations.

:Fourw'subscribers lines are shown in Fig. 14,

comprisinglines II and l2of thefirst sub-group and lines 2| and 22 of the second sub-group. The sub-station A on line I l is also shown.

The line conductors 3llll-3fil of line H extend from sub-station A to theexchange, where they are provided with individual line equipment comprising the line relay 3G1 and the cut-off relay 35:6. The conductors 300-39! and the test conductor 302 then extend to the finder switching mechanism where they terminate in the line bars 28-2 9 and the test bar 30, respectively. These bars, it will be recalled, extend through all the trunk units of the apparatus. Outgoing calls, 17 'e., calls from the exchange to a subscriber's line such as line II are completed over the socalled. normal conductors 303-305-3535 which come fromconnectors. No connector mechanism istsh-own, but it may be of any suitable type, e. g., such as is described in Boswau Patent No. 2,307,757. Incoming calls from a subscriber to the exchange are handled as will be presently described.

The individual line equipment for lines [2, .2! and 22 is similar to the individual line equipment provided for line H.

The drawing also shows diagrammatically parts of two sets of the intermediate trunk elements at the No. l trunk unit and corresponding parts of two sets of the intermediate trunk elements at the No. 2 trunk unit.

Two of the tens solenoids are indicated at l25--l 26, and two units solenoids are indicated at I'm-I'M. These tens and units solenoids are also part of the switching mechanism or No. .I trunk unit. The trunk or gate magnet of this trunk unit is shown in Fig. 15 at 255. The corresponding trunk or gate magnet of trunk unit No.2 appears at 265a.

One of the tens actuators at No. l trunk unit is indicatedin Fig. 14 at 95, and a units actuator is indicated in Fig. 15 at I63. The selection of the tens actuator depends on the enengization of the tenssolenoid I25, and the selection of the units actuator I68 depends on the actuation of the units solenoid I73. The operation of both actuators depends on the energization of the trunk or gate magnet 205.

Equipment at the test unit includes the tens actuator 255, the operating magnet 26% and two of thertens solenoids 1H5 and 322. The tens solenoid 3l5 coacts with the tens actuator 255, which serves the first sub-group (lines ll, 12, etc.) and thetenssolenoid 322 coacts with a similar actuator provided in the test unit for the second subgroup (lines 2!, 22, etc.).

.RelaysSEl-EEZ, shown at the right end of Fig. 15, are the'trunk distributor relays for the No. l' andNo. 2. trunk units, respectively. A similar relay is provided for each remaining trunk unit. The operated position of any one of these relays servesas a criterion that the trunk line terminating in the corresponding trunk unit is idle and selectable. When a trunk line is seized, itstrunk distributing relay is deenergized. The operationof the various trunk distributor relays determines the sequence with which the trunk lines are put in service. Relay 35| is a common relay for resetting the trunk distributor relays.

Relays tit-342, shown at the left of Fig. 15, are the-trunk test relays forthe No. l and No. 2 trunkunits, respectively. Each of the remaining trunk. units is provided with a similar test relay. Associated with the trunktest relays is thestart relay 1350. 1 

